Method and device for controlling route and computer program therefor

ABSTRACT

A method for controlling routes in a network which is temporarily formed among a plurality of nodes. The method includes the steps of broadcasting a discovery demand of a destination node; receiving a first reply from the destination node with respect to the discovery demand; referring a joint count contained in the first reply and registering the joint count in a node which received the reply; adding 1 to the joint count if there is a plurality of nodes forming a plurality of links to which the reply is transferred, and transmitting the reply to each of the links, and selecting one of the links having a smaller registered joint count as a route if there is a plurality of links through which the data is transmitted to the destination node.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and a device for controllingroutes, and to a computer program used for controlling the routes. Morespecifically, the present invention relates to a method, a device, andcomputer program for controlling routes used in a network which istemporary formed among a plurality of nodes, such as a so-calledmulti-hop network.

2. Description of Related Art

Research and development in so-called multi-hop (or ad hoc) networkshave began. A multi-hop network is a network formed by a plurality ofnodes, each of which functioning as a router. For example, a homenetwork which is temporarily formed among a plurality of terminalscapable of short range communication and in which information consumerelectronics are mutually connected by wireless communication calledBluetooth, and a temporary network formed in a conference are presumedto be multi-hop networks.

Here, examples of system used in such networks will be brieflyexplained. As shown in FIG. 9, routes from the node S from which dataare transmitted (hereinafter also referred to as a transmission sourcenode) to the node D to which the data are sent (hereinafter alsoreferred to as a destination node) are supplied through nodes N1-N4which relay data packets. In the case shown in FIG. 9, if the node N1moves outside of the network, the link between the node N1 and the nodeS is broken. However, since the route connecting S, N3, N4, and D isstill available, it is possible to connect the node S to the node D byselecting this route while restoring the disconnected route.

On the other hand, if the link between the nodes S and N1 is overlappedas shown in FIG. 10 (in comparison with FIG. 9), all of the routes willbe disconnected and cannot be restored if the link between the nodes Sand N1 is broken. For this reason, it is necessary to control routes sothat the routes will be formed with as few overlapping links as possibleas shown in FIG. 9.

As methods for controlling routes in an ad hoc network, Dynamic SourceRouting (DSR) method and Ad hoc On-demand Distance Vector Protocol(AODV), for example, are available. Also, a method obtained by expandingthe AODV, which is called Ad hoc On-demand Multipath Distance VectorProtocol (AOMDV) has been proposed (refer to M. K. Marina and S. R. Das,“In Proceedings of the International Conference for Network Protocol”,November 2001).

The AOMDV is a protocol for forming a plurality of routes which do notcontain overlapped links such as the one shown in FIG. 10. Here, theprocedure for forming routes using the AOMDV will be explained withreference to FIG. 11. First, the node S broadcasts a message (RREQ) forsearching the node D. The message contains an area in which the addressof the node which first receives the message will be registered, andnothing is registered at this area when the message is transmitted fromthe node S. The nodes N1 and N2 which received the message recognizethat they are the nodes which first received the message, and registersthe address thereof in the above-mentioned area. Then, the nodes N1 andN2 broadcast the message. The node I which received the message fromboth the nodes N1 and N2, only acquires the message which is receivedearlier, i.e., the message from N1 in the figure, and abandons the othermessage, i.e., the message from N2. Then, the node I broadcasts themessage, and the message is transmitted to the node D via the nodes N3and N4 to establish the transfer routes. The node D unicasts a replymessage (RREP) to the nodes N3 and N4 which broadcasted the message, andthereafter each of the nodes unicasts a reply message to the node whichbroadcasted the message to establish feedback routes which are reverseof the transfer routes.

The above-mentioned AOMDV has the following characteristics. Although amessage received later is normally abandoned unconditionally if abroadcasted message is received in duplicate, in the AOMDV method, thereceiving node (I) refers to the above-mentioned address registrationarea in the message, and if the address is different from the message(N1) which is already received, a process for renewing the feedbackroutes is performed, i.e., the node (I) unicasts a RREP to the sourcenode of transmitting the message. In this manner, the node I establishesdistinct links N1 and N2 and becomes a relay node at which the two linkscross over. As a result, a plurality of routes having no overlappedlinks are established.

However, in the above-mentioned method, there are the followingproblems. That is, as shown in FIG. 12, if a plurality of relay nodes Xand Y which correspond to the node I and at which plural links crossover, are present, an overlapped link connecting X-N3-Y is generatedbetween the relay nodes X and Y. The reason for the formation of thisoverlapped link is as follows. The node X, when it receives a RREQmessage from the nodes N1 and N2, broadcasts only the message (N1) whichis received first. Although the message is broadcasted to the node Y viathe nodes N3 and N4, the node Y unconditionally abandons the messagewhich is received later since the addresses thereof are the same (N1).As a result, the route which passes through the node N4 is notestablished, and the above-mentioned overlapped link is generated.

BRIEF SUMMARY OF THE INVENTION

The present invention was made in consideration of the above situation,and an object of the invention is to provide a method and a device, anda computer program, each of which enables establishing and selectingroutes having few overlapped links and overlapped nodes in a networkwhich is temporary formed among a plurality of nodes, such as an ad hocnetwork.

In order to achieve the above object, the first aspect of the presentinvention provides a method for controlling routes in a network which istemporary formed among a plurality of nodes, comprising the steps ofbroadcasting a discovery demand of a destination node; receiving a firstreply from the destination node with respect to the discovery demand;referring a joint count contained in the first reply and registering thejoint count in a node which received the reply; adding 1 to the jointcount if there is a plurality of nodes forming a plurality of links towhich the reply is transferred, and transmitting the reply to each ofthe links, and selecting one of the links having a smaller registeredjoint count as a route if there is a plurality of links through whichthe data is transmitted to the destination node. Also, if a certainroute is cut or disconnected, it becomes possible to quickly select analternative route by referring to the joint count.

According to the above method, it becomes possible to create and/orselect a route having few overlapped links or nodes by avoiding a routein which a plurality of links are connected to one node because thejoint count is increased when there is a plurality of links to which theabove reply is transmitted, i.e., when a plurality of links areconnected to one node, and a route having a smaller joint count isselected.

In another aspect of the present invention, it is preferable that theabove method further comprises the step of renewing the registered jointcount when a second reply is received after receiving the first reply ifa joint count contained in the second reply is larger than the jointcount contained in the first reply.

According to the above method, the state of the network can beaccurately reflected to the joint count and the route selection can beaccurately carried out based on the joint count since the largest jointcount is registered in the node which received the reply.

In yet another aspect of the present invention, it is preferable thatthe above method further comprises the step of transmitting an errormessage informing of the breaking of a link if a breaking of a link isdetected, wherein it is controlled not to transmit the error message ifan alternative route is available to transmit the data to thedestination node.

According to the above method, it becomes possible to prevent problems,such as increase in traffic in the network and useless data processingin each node, which may be caused when all of the nodes which receivedthe error message transmit the message.

The present invention also provides a device which controls routes in anetwork which is temporarily formed among a plurality of nodes, thedevice being provided in each of the nodes, comprising a broadcastingunit which broadcasts a discovery demand of a destination node; areceiving unit which receives a first reply from the destination nodewith respect to the discovery demand; a registering unit which refers ajoint count contained in the first reply and registers the joint count;a transmitting unit which adds 1 to the joint count if there is aplurality of nodes forming a plurality of links to which the reply istransferred, and transmits the reply to each of the links, and aselecting unit which selects one of the links having a smallerregistered joint count as a route if there is a plurality of linksthrough which the data is transmitted to the destination node.

The present invention also provides a computer-readable medium encodedwith a computer program which executes the steps of broadcasting adiscovery demand of a destination node; receiving a first reply from thedestination node with respect to the discovery demand; referring a jointcount contained in the first reply and registering the joint count in anode which received the reply; adding 1 to the joint count if there is aplurality of nodes forming a plurality of links to which the reply istransferred, and transmitting the reply to each of the links, andselecting one of the links having a smaller registered joint count as aroute if there is a plurality of links through which the data istransmitted to the destination node.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Some of the features and advantages of the invention having beendescribed, others will become apparent from the detailed descriptionwhich follows, and from the accompanying drawings, in which:

FIG. 1 is a schematic block diagram showing the structure of a node(terminal) which forms a temporary network;

FIG. 2 is a diagram showing a format of a discovery demand message(RREQ) of a destination node;

FIG. 3 is a diagram showing a format of a reply message (RREP) to theRREQ;

FIG. 4 is a diagram showing basic procedure for controlling routescarried out by a node;

FIG. 5 is a diagram showing the structure of entire network formed bythe nodes;

FIG. 6 is a flowchart showing the procedure carried out by each of thenodes which received the RREP;

FIG. 7 is a diagram showing joint counts set for each of the links;

FIG. 8 is a diagram for explaining a procedure for selecting analternative route when a route is disconnected;

FIG. 9 is a diagram for explaining a conventional route selection in amulti-hop network;

FIG. 10 is another diagram for explaining a conventional route selectionin a multi-hop network;

FIG. 11 is yet another diagram for explaining a conventional routeselection in a multi-hop network; and

FIG. 12 is yet another diagram for explaining a conventional routeselection in a multi-hop network.

DETAILED DESCRIPTION OF THE INVENTION

The invention summarized above and defined by the enumerated claims maybe better understood by referring to the following detailed description,which should be read with reference to the accompanying drawings. Thisdetailed description of particular preferred embodiments, set out belowto enable one to build and use one particular implementation of theinvention, is not intended to limit the enumerated claims, but to serveas a particular example thereof.

Hereinafter, embodiments of the present invention will be explained withreference to the accompanying drawings. FIG. 1 is a block diagramshowing an example of the structure of a node (terminal) whichtemporarily forms a network to which the present invention is applied.Note that in this embodiment, it is assumed that each of the nodes mayfunction as a transmission source node S, a destination node D, and a(relay) node N.

As shown in FIG. 1, each of the nodes includes a control unit (routecontrolling device) 2 which controls the entire node, an application(computer program) 4, a protocol unit 6, a routine-performing unit 8, awireless communication unit 10, and a route controlling table 12. In theapplication 4, various processes carried out in the present inventionare recorded. The protocol unit 6 performs a predetermined protocolcontrol. The routine-performing unit 8 performs a routine program of acomputer. The wireless communication unit 10 is used to make wirelesscommunication with the other nodes via a wireless communication antenna10 a. The route controlling table 12 is used to register variousinformation for controlling routes.

FIG. 2 is a diagram showing an example of the format of a discoverydemand message (RREQ) of a destination node, and FIG. 3 is a diagramshowing an example of the format of a reply message (RREP) correspondingto the RREQ. In FIG. 2, the RREQ includes an IP header, a UDP header,and an AODVM (AODV based Multipath routing) message used in the presentinvention. In the IP header, an address of the RREQ source (Source IPaddress) is recorded. Also, the Destination IP address and theOriginator IP address contained in the AODVM message define thedestination (D) and the source (S), respectively. These formats are thesame as those used in the conventional AODV.

In FIG. 3, the RREP includes an IP header, a UDP header, and an AODVMmessage, and addresses of the RREP source (Source IP address andDestination IP address) are recorded in the IP header. Note that thecharacteristics of the present invention include to provide a jointcount field in the AODVM message as shown in the figure. This will beexplained in detail later.

Next, basic procedures for controlling routes performed by a node whichreceived the above-mentioned RREQ or RREP will be explained withreference to FIG. 4. A case is considered where routes are createdbetween the transmission source node S and the destination node D viathe relay nodes NA and NB as shown in the figure. First, the node Sbroadcasts the RREQ. The RREQ is transferred to the node D via the nodesNA and NB in this order. At that time, each of the nodes NA and NBregisters the following information as “feedback routes” in its routecontrolling table 12A and 12B, respectively. The feedback route is usedto return to the node S, and “S” is registered in the item of“Dest(ination)” and the node from which the RREQ was received isregistered in the item of “Next hop”. The IP header of the RREQ isreferred to determine from which node the RREQ was received.

On the other hand, the node D, when it receives the RREQ, transmits(unicasts) the RREP to the source node which is obtained from the IPheader of the RREQ. The RREP reaches the node S via the nodes NB and NAin this order. At that time, each of the nodes NA and NB registers thefollowing information as “transfer routes” in its route controllingtable 12A and 12B, respectively. The transfer route is used to send datato the node D, and “D” is registered in the item of “Des(tination)” andthe node from which the RREP was received is registered in the item of“Next hop”. The IP header of the RREP is referred to determine fromwhich node the RREP was received. When the feedback route and thetransfer route are obtained as explained above, routes between the nodesare formed.

Next, control of routes in an actual network will be explained withreference to FIG. 5. FIG. 5 is a diagram showing the overall structureof a network formed by a plurality of nodes. In FIG. 5, the network isformed by the nodes S, D and a plurality of relay nodes N10-N16. Links(wireless communication network) formed between each of the nodes areindicated by solid lines.

In the network shown in FIG. 5, when the node S broadcasts the RREQ,each of the nodes records node(s) which becomes the route (feedbackroute) to the node S in its route controlling table based on thereceived RREQ. Each of the arrows S shown in FIG. 5 indicates a feedbackroute for each of the nodes, and the node(s) which becomes the route tothe node S is indicated by the pointing direction of the arrow. When theRREQ is broadcasted to the node D, the node D transmits (unicasts) theRREP. The RREP reaches the node S when each of the nodes transfers thereceived RREP to the node S using the already established feedbackroute. At that time, each of the nodes records node(s) which becomes theroute (transfer route) to the node D in its route controlling tablebased on the received RREP. Each of the arrows D shown in FIG. 5indicates a transfer route for each of the nodes, and the node(s) whichbecomes the route to the node D is indicated by the pointing directionof the arrow. In the manner shown in FIG. 5, both the feedback route andthe transfer route are always formed between each of the nodes. That is,according to the embodiment of the present invention, since a RREQreceived later is not abandoned based on the address registry area inthe RREQ as in the conventional AOMDV, there is no danger that anoverlapped route will be formed due to a non-formation of a routebetween nodes.

However, in the case where created routes are randomly used, simpleplural routes are formed and some of which may contain overlapped links.Accordingly, the following process is provided in the embodiment of thepresent invention so that a route which does not contain overlappedlinks can be selected.

In this process, each of the nodes carries out the procedure shown inthe flowchart of FIG. 6. In the flowchart shown in FIG. 6, each of thenodes N10-N16 first receives the RREP (step S1). In the RREP, the jointcount field shown in FIG. 3 is provided, and each of the nodes refersthe value (the joint count) thereof (step S3). Here, the joint count isset to be zero whenever the destination node D transmits the RREP. Eachof the nodes registers the referred value (the referred joint count) foreach transfer route in the route controlling table (step S5).

Then, each of the nodes determines whether there are a plurality offeedback routes to which the RREP should be transmitted, by referring tothe route controlling table thereof (step S7). Here, it is determinedwhether plural nodes are registered in the item of “Next hop” of thefeedback route. If the result is “Yes” in step S7, each of the nodesadds “1” to the value of the joint count field of the RREP, andtransmits the resultant value to the next node (Next hop) (step S9). Onthe other hand, if the result is “No” in step S7, each of the nodestransmits the RREP of original value (i.e., the referred joint count) tothe next node (step S11).

Each of the following Tables 1 and 2 shows data of the route controllingtable of each node used in the procedure shown in the flowchart of FIG.6. Tables 1 and 2 are data of route controlling tables of nodes N16 andN14, respectively, shown in FIG. 5.

TABLE 1 Route controlling table of N16 Dest Next hop Joint countTransfer route D D 0 Feedback route S N13 S N15

TABLE 2 Route controlling table of N14 Dest Next hop Joint countTransfer route D N13 2 Feedback route D N15 1 S S

In the Table 1, the joint count contained in the RREP is zero since thenode N16 directly receives the RREP form the node D. Accordingly, “0” isregistered in the “Joint count” field of the transfer route (thetransmitting route to the node D). On the other hand, there are twofeedback routes for the node N16, one is to the node N13 and the otheris to the node N15. Accordingly, the result of determination in theabove-mentioned step S7 will be “Yes”. Therefore, the node N16 transmitsthe RREP having the joint count of “1” (i.e., 1 is added to 0) to eachof the nodes N13 and N15.

Also, in Table 2, the node N14 receives the RREP from each of the nodesN13 and N15. Here, as shown in FIG. 7, the joint count of the RREPtransmitted from the node N13 is 2, and the joint count of the RREPtransmitted from the node N15 is 1. Accordingly, among the transferroutes (transmitting routes to the node D), the “next hop” registers “2”in the “joint count” field of the node N13, and the “next hop” registers“1” in the “joint count” field of the node N15. On the other hand, thefeedback route for the node N14 is only one, and the result ofdetermination in the above-mentioned step S7 becomes “No”. Accordingly,the node N14 transmits the RREP whose joint count has not been changedto the node S.

In the case where a plurality of transfer routes exist, as it does forthe node N14, there may occur the following problems. That is, since thenodes that transmit the RREP to the node S are overlapped by the numberof the transfer routes, there is a problem for the node S regardingwhich value of the joint count should be registered that is contained inthe RREP received from each of the nodes. Accordingly, the receivingnode (S) of the RREP, when it received a RREP after receiving anotherRREP, changes the joint count if the joint count contained in the RREPreceived later is larger than the joint count already registered in thetable. In this manner, the state of the network is accurately reflectedto the joint count since the largest joint count is registered in thereceiving node of the RREP, and hence, a route selection based on thejoint count can be accurately carried out.

In accordance with the procedure explained above, the joint count foreach transfer route is registered in the table of each node as shown inFIG. 7. Note that in FIG. 7, the nodes N10 and N14, for example, arepresent as transfer routes for the node S. This is indicated by each ofthe arrows D shown in the figure, and the number shown in parentheses,e.g., 2, indicates the joint count.

Next, a method for selecting a route using the joint count shown in theabove-mentioned FIG. 7 will be explained. First, the node S refers toits route controlling table and transfers data (packet) which istransmitted to the destination node D, using one of the two transferroutes of the node N10 and the node N14 which has a fewer joint count.In this embodiment, since the joint count of both of the transfer routesis the same value (i.e., 2), the node S randomly determines the transferroute. In FIG. 7, it is assumed that the transfer route {circle around(1)} (i.e., N10) is selected.

Then, the node N10 which received the data refers to the routecontrolling table thereof, and transfers the data using one of the twotransfer routes of the node N11 and the node N14 having lower jointcount. In this embodiment, since the joint count of the transfer routepassing through the node N11 is lower, the transfer route {circle around(2)} is selected.

For the case of the nodes N11 and N12, respectively, since there is onlyone transfer route for each of the nodes, the transfer routes {circlearound (3)} and {circle around (4)}, respectively, are selected. In thismanner, the route {circle around (1)}-{circle around (4)} shown in thefigure is selected. Note that this route is the route having the lowestprobability of causing problems, such as breaking or disconnection ofthe route, since the route contains no overlapped links and nooverlapped relay nodes. Similarly, in the case shown in the figure, theroute of S-N14-N15-N16-D also does not contain overlapped links andoverlapped relay nodes.

In the meantime, when the route is cut or disconnected, the nodebelonging to the disconnected link broadcasts an error message whichinforms the generation of disconnection using the feedback route.However, there is a danger of increasing traffic of the network orgenerating useless data processing in each node if all of the nodes thatreceived the error message sequentially broadcast the error message.Accordingly, in this embodiment of the present invention, a transmissioncontrol of an error message is carried out as shown in FIG. 8.

In the case shown in FIG. 8, it is assumed that the link between thenodes N12 and D is disconnected (route 1) as indicated by a crossingmark. The node N12 which belongs to the disconnected link detects thedisconnection and broadcasts an error message (indicated by the arrows Ein the figure). Here, the broadcast of 1HOP is considered. The node N11which received the message from the node N12, refers to the routecontrol table thereof, and recognizes that the number of transfer routesis one (from the node 11 to the node N12). It has been set that eachnode broadcasts an error message when there is only one transfer route,i.e., when there is no alternative route for avoiding the disconnectedlink, and hence, the node N11 broadcasts the error message. Also, thenode N11 flags the transfer route contained in the route controllingtable indicating that the route is disconnected.

The node N13 which received the error message from the node N12, on theother hand, refers the route controlling table thereof, and recognizesthat there are two transfer routes (i.e., from N13 to N12, and from N13to N16). Since it has been set that each node does not broadcasts anerror message, and selects an alternative route which does not passesthrough the disconnected link when there are two or more transferroutes, the node N13 does not broadcast the error message. Similarly,the node N10 which received the error message from the node N11 does notbroadcast the error message since there are two transfer routes (i.e.,from N10 to N11, and from N10 to N13). In this manner, it becomespossible to decrease the number of broadcastings of the error message tothe lowest level. Note that the nodes N13 and N10 give a flag to thedisconnected route among the transfer routes contained in the routecontrolling table thereof.

Next, a method for selecting an alternative route based on theabove-mentioned error message will be explained. First, the node Srandomly selects a route from the two transfer routes of the nodes N10and N1 4 having the same joint count, and transfers the data which istransmitted to the destination node D in the same manner as explainedfor the above-mentioned FIG. 7. Here, if the route passing through thenode N14 is selected, the route 3 of S-N14-N15-N16-D shown in FIG. 8 inwhich no overlapped links and no overlapped nodes are present will beselected as explained above. On the other hand, if the route passingthrough the node N10 is selected, the node N10 refers to the flag of thetransfer route contained in the route controlling table, and recognizesthat the route through the node N11 has been disconnected. Accordingly,the node N10 selects a transfer route which has no flag (i.e., the routethrough the node N13), and transfers the data thereto. Similarly, thenode N13 which received the data refers to the route controlling tableand selects a route having no flag (i.e., the route through the nodeN16) so that the data will be transferred through the selected route.Then, the node N16 transfers the data to the node D. In this manner, theroute 2 shown in FIG. 8 is selected.

Note that the method for controlling routes according to the presentinvention may be realized by using a computer, various accessories, suchas a communication device, and a software program which is executed bythe computer. The software program which is executed in the above systemmay be distributed through a computer readable storage medium orcommunication network.

Having thus described several exemplary embodiments of the invention, itwill be apparent that various alterations and modifications will readilyoccur to those skilled in the art. Such alterations and modifications,though not expressly described above, are nonetheless intended andimplied to be within the spirit and scope of the invention. Accordingly,the foregoing discussion is intended to be illustrative only, theinvention is limited and defined only by the following claims andequivalents thereto.

1. A method for controlling routes in a network for transmittinginformation from a source to a destination which network temporarilyformed among a plurality of nodes between the source and destination,comprising the steps of: broadcasting a discovery demand of thedestination node and each node of the plurality of nodes; receiving afirst reply from said destination node with respect to the discoverydemand; referring a joint count contained in the first reply andregistering the joint count in one of the nodes which received thereply; adding 1 to the joint count when it is determined that there is aplurality of nodes forming a plurality of links to said each node of theplurality of nodes, and transmitting the reply to each of the links; andselecting one of the routes having a smaller registered joint count as atransmission route for the transmission of information if there is aplurality of routes through which the data is transmitted to saiddestination node.
 2. A method for controlling routes according to claim1, further comprising the step of: renewing the registered joint countwhen a second reply is received after receiving the first reply if ajoint count contained in the second reply is larger than the joint countcontained in the first reply.
 3. A method for controlling routesaccording to claim 1 or 2, further comprising the step of: transmittingan error message informing of a disconnection of any of the links if adisconnection of a link is detected, wherein it is controlled not totransmit the error message if an alternative route is available totransmit the data to said destination node.
 4. A device which controlsroutes in a network for transmitting information from a source to adestination which network is temporarily formed among a plurality ofnodes between the source and destination, said device being provided ineach of the nodes and comprising: a broadcasting unit which broadcasts adiscovery demand of the destination node and each of the plurality ofnodes; a receiving unit which receives a first reply from saiddestination node with respect to the discovery demand; a registeringunit which refers a joint count contained in the first reply andregisters the joint count; a transmitting unit which adds 1 to the jointcount when it is determined that there is a plurality of nodes forming aplurality of links to said each of the plurality of nodes, and transmitsthe reply to each of the links, and a selecting unit which selects oneof the routes having a smaller registered joint count as a transmissionroute for the transmission of information if there is the plurality oflinks through which the data is transmitted to said destination node. 5.A computer-readable medium encoded with a computer program includinglogic which executes the steps of: broadcasting a discovery demand ofthe destination node and each node of the plurality of nodes; receivinga first reply from said destination node with respect to the discoverydemand; referring a joint count contained in the first reply andregistering the joint count in a node which received the reply; adding 1to the joint count when it is determined that there is a plurality ofnodes forming a plurality of links to said each node of the plurality ofnodes, and transmitting the reply to each of the links, and selectingone of the links having a smaller registered joint count as atransmission route for the transmission of information if there is theplurality of links through which the data is transmitted to saiddestination node.
 6. A method for controlling routes according to claim1, further comprising the step of: transmitting information from saideach node of the plurality of nodes to a subsequent node in the selectedone route.
 7. The device of claim 4, where the transmitting unittransmits information from said each node of the plurality of nodes toanother of the plurality of nodes, in the selected route.
 8. Thecomputer readable medium of claim 5, wherein the logic executes the stepof: transmitting information from said each node of the plurality ofnodes to a subsequent node in the selected one route.